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Date:   Tue, 30 Apr 2019 10:19:22 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc:     linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v3 12/16] PM / devfreq: tegra: Reconfigure hardware on
 governor's restart

Hi,

On 19. 4. 18. 오전 7:29, Dmitry Osipenko wrote:
> Move hardware configuration to governor's start/resume methods.
> This allows to re-initialize hardware counters and reconfigure
> cleanly if governor was stopped/paused. That is needed because we
> are not aware of all hardware changes that happened while governor
> was stopped and the paused state may get out of sync with reality,
> hence it's better to start with a clean slate after the pause. In
> a result there is no memory bandwidth starvation after resume from
> suspend-to-ram that results in display controller underflowing that
> happens on resume because of improper decision made by devfreq about
> the required memory frequency. This change also cleans up code a tad
> by moving hardware-configuration code into a single location.
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/devfreq/tegra-devfreq.c | 98 ++++++++++++++-------------------
>  1 file changed, 40 insertions(+), 58 deletions(-)
> 
> diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c
> index 62f35e818122..e9ab49394d35 100644
> --- a/drivers/devfreq/tegra-devfreq.c
> +++ b/drivers/devfreq/tegra-devfreq.c
> @@ -392,55 +392,6 @@ static int tegra_actmon_rate_notify_cb(struct notifier_block *nb,
>  	return NOTIFY_OK;
>  }
>  
> -static void tegra_actmon_enable_interrupts(struct tegra_devfreq *tegra)
> -{
> -	struct tegra_devfreq_device *dev;
> -	u32 val;
> -	unsigned int i;
> -
> -	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
> -		dev = &tegra->devices[i];
> -
> -		val = device_readl(dev, ACTMON_DEV_CTRL);
> -		val |= ACTMON_DEV_CTRL_AVG_ABOVE_WMARK_EN;
> -		val |= ACTMON_DEV_CTRL_AVG_BELOW_WMARK_EN;
> -		val |= ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN;
> -		val |= ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN;
> -
> -		device_writel(dev, val, ACTMON_DEV_CTRL);
> -	}
> -
> -	actmon_write_barrier(tegra);
> -}
> -
> -static void tegra_actmon_disable_interrupts(struct tegra_devfreq *tegra)
> -{
> -	struct tegra_devfreq_device *dev;
> -	u32 val;
> -	unsigned int i;
> -
> -	disable_irq(tegra->irq);
> -
> -	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
> -		dev = &tegra->devices[i];
> -
> -		val = device_readl(dev, ACTMON_DEV_CTRL);
> -		val &= ~ACTMON_DEV_CTRL_AVG_ABOVE_WMARK_EN;
> -		val &= ~ACTMON_DEV_CTRL_AVG_BELOW_WMARK_EN;
> -		val &= ~ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN;
> -		val &= ~ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN;
> -
> -		device_writel(dev, val, ACTMON_DEV_CTRL);
> -
> -		device_writel(dev, ACTMON_INTR_STATUS_CLEAR,
> -			      ACTMON_DEV_INTR_STATUS);
> -	}
> -
> -	actmon_write_barrier(tegra);
> -
> -	enable_irq(tegra->irq);
> -}
> -
>  static void tegra_actmon_configure_device(struct tegra_devfreq *tegra,
>  					  struct tegra_devfreq_device *dev)
>  {
> @@ -464,11 +415,47 @@ static void tegra_actmon_configure_device(struct tegra_devfreq *tegra,
>  		<< ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_NUM_SHIFT;
>  	val |= (ACTMON_ABOVE_WMARK_WINDOW - 1)
>  		<< ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_NUM_SHIFT;
> +	val |= ACTMON_DEV_CTRL_AVG_ABOVE_WMARK_EN;
> +	val |= ACTMON_DEV_CTRL_AVG_BELOW_WMARK_EN;
> +	val |= ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN;
> +	val |= ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN;
>  	val |= ACTMON_DEV_CTRL_ENB;
>  
>  	device_writel(dev, val, ACTMON_DEV_CTRL);
> +}
> +
> +static void tegra_actmon_start(struct tegra_devfreq *tegra)
> +{
> +	unsigned int i;
> +
> +	disable_irq(tegra->irq);
> +
> +	actmon_writel(tegra, ACTMON_SAMPLING_PERIOD - 1,
> +		      ACTMON_GLB_PERIOD_CTRL);
> +
> +	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++)
> +		tegra_actmon_configure_device(tegra, &tegra->devices[i]);

nitpick.
I agree this patch.

In order to make it more simple, I think that you can remove
tegra_actmon_configure() function and then just do some opertion
under the for loop in the tegra_actmon_start() to keep
similar style with tegra_actmon_stop(). But there is perfect solution.
If you agree, edit it on next patch. If you think that it is not necessary,
just keep this code.

> +
> +	actmon_write_barrier(tegra);
> +
> +	enable_irq(tegra->irq);
> +}
> +
> +static void tegra_actmon_stop(struct tegra_devfreq *tegra)
> +{
> +	unsigned int i;
> +
> +	disable_irq(tegra->irq);
> +
> +	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
> +		device_writel(&tegra->devices[i], 0x00000000, ACTMON_DEV_CTRL);
> +		device_writel(&tegra->devices[i], ACTMON_INTR_STATUS_CLEAR,
> +			      ACTMON_DEV_INTR_STATUS);
> +	}
>  
>  	actmon_write_barrier(tegra);
> +
> +	enable_irq(tegra->irq);
>  }
>  
>  static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
> @@ -580,22 +567,22 @@ static int tegra_governor_event_handler(struct devfreq *devfreq,
>  	switch (event) {
>  	case DEVFREQ_GOV_START:
>  		devfreq_monitor_start(devfreq);
> -		tegra_actmon_enable_interrupts(tegra);
> +		tegra_actmon_start(tegra);
>  		break;
>  
>  	case DEVFREQ_GOV_STOP:
> -		tegra_actmon_disable_interrupts(tegra);
> +		tegra_actmon_stop(tegra);
>  		devfreq_monitor_stop(devfreq);
>  		break;
>  
>  	case DEVFREQ_GOV_SUSPEND:
> -		tegra_actmon_disable_interrupts(tegra);
> +		tegra_actmon_stop(tegra);
>  		devfreq_monitor_suspend(devfreq);
>  		break;
>  
>  	case DEVFREQ_GOV_RESUME:
>  		devfreq_monitor_resume(devfreq);
> -		tegra_actmon_enable_interrupts(tegra);
> +		tegra_actmon_start(tegra);
>  		break;
>  	}
>  
> @@ -664,15 +651,10 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
>  	tegra->max_freq = clk_round_rate(tegra->emc_clock, ULONG_MAX) / KHZ;
>  	tegra->cur_freq = clk_get_rate(tegra->emc_clock) / KHZ;
>  
> -	actmon_writel(tegra, ACTMON_SAMPLING_PERIOD - 1,
> -		      ACTMON_GLB_PERIOD_CTRL);
> -
>  	for (i = 0; i < ARRAY_SIZE(actmon_device_configs); i++) {
>  		dev = tegra->devices + i;
>  		dev->config = actmon_device_configs + i;
>  		dev->regs = tegra->regs + dev->config->offset;
> -
> -		tegra_actmon_configure_device(tegra, dev);
>  	}
>  
>  	for (rate = 0; rate <= tegra->max_freq * KHZ; rate++) {
> 

I agree to always initialize the device when START or RESUME
and also to reset the device when STOP or SUSPEND.

Reviewed-by: Chanwoo Choi <cw00.choi@...sung.com>

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics

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